Hydrocarbon conversion process with a platinum containing catalyst



HYDROCARBON CQNVERSION PROCESS WITH A PLATINUM CUNTAENING CATALYST George R. Donaldson, North Riverside, 111., assignor to Universal Gil Products Company, Des Plaines, 111., a corporation of Delaware No Drawing. Griginal applicah'on May 29, 1950, Serial No. 165,107, new Patent No. 2,723,946, dated November 15, 1955. Divided and this application June 29, 1955, Serial No. 518,971

8 Claims. (Cl. 196-50) This application is a division of my copending applica tion Serial No. 165,107, filed May 29, 1950, now Patent No. 2,723,946, November 15, 1955.

This invention relates to the catalytic conversion of hydrocarbons. It is more specifically concerned with a method of reforming hydrocarbon fractions boiling approximately within the gasoline range.

Recently, a superior reforming catalyst has been de veloped, said catalyst comprising palladium or, preferably, platinum and alumina as the principal constituents and frequently containing minor amounts of a halogen, particularly fluorine or chlorine. Catalysts of this type are capable of increasing the octane number of hydrocarbon stocks such as straight-run gasolines and naphthas to values that are substantially higher than those that ordinarily can be reached by thermal reforming. In addition, the yield-octane number relationship is much better than are the corresponding relationships obtained in either thermal reforming or in most of the prior catalytic reforming processes. it has been found that by an appropriate selection of operating conditions and by charging a feed stock of relatively low end point, these catalysts can be used for a number of weeks or months without regeneration. However, if the end point of the charge stock is relatively high, for example, higher than about 400 F. or if the charging stock contains minor traces of impurities, such as nitrogen compounds, which tend to deactivate or poison the catalyst, the rate of catalyst de activation is greatly accelerated. In order that this process be economically attractive it is desirable that it be substantially nonregenerative. I have invented a process by means of which greatly increased catalyst life is obtained with poor stocks as well as with good stocks.

it is an object of this invention to convert gasoline boiling range hydrocarbons to more valuable products.

Another object of this invention is to reform low octane number hydrocarbon fractions to products of higher octane number.

Still anothcr object of this invention is to reform in substantially nonregenerative operation in the presence of platinumor palladium-containing catalysts gasoline fractions that tend to relatively rapidly deactivate said catalyst.

in one embodiment my invention relates to an improvement in the conversion of a hydrocarboncharge stock in the presence of a catalyst selected from the group consisting of platinumand palladium-containing catalyst at conversion conditions at which the charge stock tends to deactivate the catalyst, said improvement comprising processing said stock until the catalyst has lost 2,838,446 Patented June 10, 1958 a measurable amount of activity, discontinuing the processing of said charge stock and substituting therefor ahydrocarbon charge stock which exhibits less tendency to deactivate the fresh catalyst, processing said latter stock until at least a part of the lost activity has been restored, and thereafter discontinuing the processing of said latter stock and processing a charge stock which tends to de-' activate the catalyst.

In another specific embodiment my invention relates to an improvement in the reforming of hydrocarbon charge stocks boiling approximately within the gasoline range and having an appreciable nitrogen compound content at reforming conditions at which the charge stock exhibits a substantial tendency to deactivate the catalyst, the im provement which comprises reforming said stock until the catalyst has lost a measurable amount of activity, discontinuing the reforming of said charge stock and sub stituting therefor. a normally liquid hydrocarbon charge stock substantially free from nitrogen compounds which exhibits less tendency to deactivate the fresh catalyst, reforming said latter stock until at least part of the lost activity has been restored, and thereafter discontinuing the processing of said latter stock and resuming the processing of a stock having ahigher nitrogen content.

In the hydrocarbon reforming processes employing a catalystcomprising platinum and alumina or palladium and alumina, the hydrocarbon reactant to be converted is preheated. and, together with hydrogen, is contacted with the catalyst. As is usual in catalytic processes of this type, the hydrocarbon conversion reaction ordinarily is accompanied by a. fouling reaction which causes deposition of carbonaceous material, hereinafter called carbon on the catalyst. The presence of the deposit lowers the activity of the catalyst and in the usual operation a point is reached at which the effectiveness of the catalyst is so low that it. must either be discarded and replaced with fresh catalyst, or the activity of the catalyst must be restored by the removal of the carbon by combustion. Both methods are expensive, and it can be readily seen that substantial economic and operating advantages wouldaccrue if it were possible to hinder or retard carbon formation, or remove carbon formed during the processing of the hydrocarbon.

l have found that the useful life of the catalyst can be greatly increased if a charging stock that exhibits a low tendency to foul or carbonize the catalyst is periodically substituted for the normal hydrocarbon charging stock that exhibits a greater tendency to foul the catalyst.

It has been observed that hydrocarbon fractions possessing relatively high end boiling points produce a considerably larger amount of carbon in a given amount of time than do hydrocarbon fractions having lower end boiling points. Thus, for example, the catalyst carbon production rate with a BOO-425 F. straight-run naphtha is many times higher than is the carbon pi-oductian rate at equivalent conditions with a l00-300 F. straight-run naphtha. I have found that if I- reform a relatively high boiling hydrocarbon fraction in the presence of a pal ladiumor platinum-containing catalyst, thereby depositing an appreciable 'amount of carbon on the catalyst, and thereafter reform a lower boiling fraction with the sam catalyst, that there is not merely a decrease in the rate at which carbon is deposited during the processing of the last-named fraction, but that there is an actual decrease in the amount of carbon on the catalyst. .This decrease in the carbon content of the catalyst results in at least a partial restoration of the catalyst activity. Consequently, it is possible to again switch back to the higher boiling fraction and obtain an appreciable further amount of conversion therewith. Briefly then, it can be seen that I am able to process a greater amount of higher boiling charging stocks with a given amount of catalyst by alternately processing higher boiling and lower boiling stocks, than would be possible if I processed only the higher boiling fraction.

A particularly useful application of my invention involves separating a normal wide boiling hydrocarbon reforming stock into, for example, a higher boiling fraction and a lower boiling fraction and alternately subiecting said fractions to reforming in the presence of a catalyst comprising palladiumalumina or platinumalumina. Each fraction can then be processed under the conditions most favorable for a good yield-octane number relationship for that particular fraction. In addition, the processing of the lower boiling fraction removes a certain amount of the carbon deposited on the catalyst during the processing of the higher boiling fraction. With this type of operation I can obtain markedly increased overall catalyst life as well as a superior yieldoctane number relationship.

Another type of hydrocarbon reforming charge stock that tends to deactivate catalysts of the type herein described are those hydrocarbon fractious that possess an appreciable nitrogen compound content. The nitrogen compounds appear to temporarily poison the catalyst, thereby deactivating the same. The deactivation does not appear to be due to deposition of carbonaceous material on the catalyst, since the rate of carbon formation with such stocks frequently is appreciably lower than it line from the Los Angeles Basin, I alternately process a stock that is substantially free from nitrogen compounds. In this way I am able to process a much larger amount of the nitrogen-containing stock than would otherwise be possible.

The hydrocarbon stocks that may be converted in accordance with my process comprise hydrocarbon fractions boiling approximately within the gasoline range and containing saturated hydrocarbons, particularly naphthenes. The preferred stocks are those consisting essentially of naphthenes and parafiins, although in some cases aromatics and/or olefins also may be present; This preferred class includes straight-run gasolines, natural gasolines, and the like. On the other hand, it frequently is advantageous to charge thermally or catalytically cracked gasolines, particularly higherboiling fractions thereof to my. reforming process. If a cracked gasoline or fraction is charged, it often will be processed in admixture with a straight-run fraction. The gasoline may be full boiling range gasoline having an initial boiling point of from about F. to about 100 F. and an end boiling point within the range of from about 325 F. to about 425 F., or it may be a selected fraction thereof which usually will be a higher boiling fraction, commonly referred to as naphtha, and generally having an initial boiling point within the range of from about 125 F. to about 250 F. and an end boiling point within the range of from about 350 F. to about 425 F.

The hydrocarbon stock that I use to at least partially restore the activity of the used catalyst should be one that exhibits less tendency than the first-used stock to deactivate the catalyst at substantially the same operating conditions or, preferably, at conditions to give substantially the same octane number, when employing fresh catalyst. For example, if stock A is reformed over platinum-alumina-combined halogen catalyst until there has been an appreciable loss in catalyst activity, stock B can be used to restore at least a portion of said lost activity if stock B causes less deactivation of fresh platinum-alumina-combined halogen catalyst than is brought about by stock A at conditions to give reformates of approximately the same octane number. After the catalyst is reactivated by stock B, stock A, or a charge stock having a similar tendency to deactivate the catalyst may be charged.

The reforming catalyst that may be used in my process is selected from those catalysts, comprising at least one refractory oxide composited or associated with platinum or palladium, that are capable of promoting hydrocracking of paraffins and dehydrogenation of naphthenes. A preferred type of catalyst that falls in this category is described in U. S. Patent No. 2,479,109, issued August 16, 1949. These catalysts comprise alumina, platinum, and combined halogen, especially combined fluorine and combined chlorine. They are prepared by forming a mixture of alumina and a halogen compound, the halogen being in an amount of from about 0.1% to about 1.0% by weight of said alumina on a dry basis, and thereafter compositing about 0.1% to about 1.0% platinum with the mixture, and subsequently heating the composite.

Another group of catalysts that may be used in the present process comprises a cracking component and a metal selected from the group consisting of platinum and palladium. The cracking component ordinarily will comprise silica and at least one other metal oxide, usually selected from the group consisting of alumina, zirconia, magnesia, and thoria. Another type of cracking component that may be used in these catalysts comprises alumina-boria composites. These catalysts are made, for example, by drying a composite of silica hydrogel and alumina hydrogel and thereafter incorporating into the dry composite a metal selected from the group consisting of platinum and palladium in an amount of from about 0.1% to about 1.0%. Further details concerning the preparation of catalysts of this type will be found in U. S. Patent No. 2,478,916.

Hydrocarbon reforming operations carried out in accordance with my invention ordinarily will be conducted at temperatures of from about 600 F. to about 1000 F. The pressures at which my process will be conducted will lie within the range of from about 50 to 1200 pounds per square inch, a total pressure of at least 250 pounds ordinarily is preferred. The weight hourly space velocity, defined as the weight of hydrocarbons charged per hour per weight of catalyst in the reaction zone, should lie within the range of from about 0.2 to about 40. The amount of hydrogen charged along with the hydrocarbons usually will be from about 0.5 to about 15 mols per mol of hydrocarbon. However, with certain types of charging stocks and in certain types of operations, sufficient hydrogen is produced in situ so that there is no necessity for charging external hydrogen.

The following example is given to illustrate my invention, but it is not given for purposes of limiting the generally broad scope of said invention.

Example A continuous reforming run that exceeded 2000 hours was made in a plant in which the reactor system comprised three adiabatic reactors. The catalyst comprised alumina containing 0.4% platinum, 0.20% fluorine, and 0.6% chlorine. Substantially nitrogen-free Mid-Continent straight-run naphtha and Los Angeles Basin naphtha containing an appreciable amount nitrogen compounds, were reformed in the run. The operating conditions an resylts are shown in the following table:

Charge Stock Mid-Continent S-R Los Angeles Basin Mid-Continent SR Naphtha Naphtha S-R Naphtha Period No Charge 7 72 75 76 77 78 81 82 Cat. Serv., Cumulative Hours 190 749 1, 881 1, 927 1, 955 2, 004 2, 060 2, 099 Total Pressure, p. s. i. g 700 700 700 700 700 700 700 700 HzflElC Ratio, Molal 6. 76 6. 73 7.00 7.17 7.17 7. 45 7.23 6. 96 Catalyst 'iemp., F.:

#1 ReactorIn1et 900 944 945 900 900 899 900 900 #2 Reactorlnlet 890 945 946 891 890 890 891 890 #3 Reactor-Inlet 880 946 945 881 881 880 884 881 Octane Nos.: Fl+3 cc. Tel- 57. 3 90. 4 96. 6 94. 8 82.2 83. 2 85.2 86. 5 88. 3 Engler Distillation:

IBP, F 240 106 151 172 141 123 124 113 115 385 414 416 412 402 409 405 408 413 The results of Periods 7 and 8 show that with the comparatively fresh catalyst a reformate octane number (l -1+3 cc. tetraethyl lead per gallon) of about 90.5 was obtained at the conditions indicated. The processing of the Los Angeles Basin straight-run naphtha brought about an appreciable deactivation of the catalyst. This is shown by the results of Period 76 in which the charge stock was again Mid-Continent naphtha. This period was made at substantially the same operating conditions as Periods 7 and 8. The greatly decreased activity of the catalyst is brought out by the octane numbers of the reformate. Continued operation with a Mid-Continent (substantially nitrogen-free) charge stock brought about a very substantial increase in the octane number of the reformate. The volatility characteristics of the reformate show the same trend. At the end of Period 82, a major portion of the lost catalyst activity had been recovered.

Following Period 82, a blend of Los Angeles Basin straight-run and thermally cracked gasoline was processed for a period of eight days. During this time the reactor temperatures were increased and the space velocity was decreased in order to raise the octane number of the product up to 9091. Following this eight day period of processing, the Mid-Continent stock was again charged to the unit and again the conditions were adjusted to those maintained in Periods 7, 8, and 76-82. The F-1+3 cc. Tel. octane number of the reformate increased from 68 to 81 in seven days of operation with the Mid- Continent stock at these operating conditions.

From the foregoing data, it can be seen that hydrocarbon reforming charge stocks containing nitrogen compounds deactivate platinum-alnmina-combined halogen catalysts. The data further show that substantial portions of this lost activity can be recovered by processing a substantially nitrogen-free hydrocarbon reforming stock in place of the nitrogen-containing stock. Thereafter, additional quantities of the nitrogen-containing stock can be reformed.

I claim as my invention:

1. In the reforming of a hydrocarbon charge stock boiling approximately within the gasoline range and having an appreciable nitrogen compound content in the presence of hydrogen and a platinum-containing catalyst at reforming conditions at which the charge stock exhibits substantial tendency to deactivate the catalyst, the method which comprises reforming said stock until the catalyst has lost a measurable amount of activity, discontinuing the processing of said charge stock and substituting therefor a normally liquid hydrocarbon charge stock substantially free from nitrogen compounds and which exhibits less tendency to deactivate the fresh catalyst, reforming said latter stock until at least a part of the lost activity has been restored, and thereafter discontinuing the reforming of said latter stock and reforming a charge stock boiling approximately within the gasoline range and having an appreciable nitrogen content in the presence of hydrogen.

2. The process of claim 1 further characterized in that said normally liquid hydrocarbon charge stock comprises a straight-run charge stock.

3. The process of claim 2 further characterized in that said platinum-containing catalyst comprises platinum and alumina.

4. The process of claim 2 further characterized in that said platinum-containing catalyst comprises alumina containing from about 0.1% to about 1.0% platinum and from about 0.1% to about 1.0% combined halogen.

5. The process of claim 2 further characterized in that said platinum-containing catalyst comprises alumina containing from about 0.1% to about 1.0% platinum and from about 0.1% to about 1.0% combined fluorine.

6. A process which comprises alternately reforming a charging stock boiling approximately within the gasoline range containing an appreciable nitrogen compound content and a charging stock boiling approximately within the gasoline range that is substantially free from nitrogen compounds at reforming conditions in the presence of a catalyst comprising alumina containing from about 0.1% to 1% platinum.

7. A process for the treatment of relatively high nitrogen compound content and relatively low nitrogen compound content fractions boiling approximately within the gasoline range, the former fraction deactivating the catalyst more than the latter fraction during catalytic reforming, which comprises reforming the former gasoline fraction in the presence of hydrogen and a platinumcontaining catalyst until the activity of the catalyst has been lowered, then discontinuing the contacting of the former fraction with said catalyst and substituting the latter fraction therefor, reforming the latter fraction in contact with said catalyst and in the presence of hydrogen until at least a portion of the catalyst activity has been restored to'the catalyst, thereafter discontinuing the reforming of the latter fraction in contact with said catalyst and resuming the reforming of a gasoline fraction of higher nitrogen compound content in contact with the catalyst.

8. In the reforming of a hydrocarbon charge stock boiling approximately Within the gasoline range and having an appreciable nitrogen compound content in the presence of hydrogen and a platinum-containing catalyst at reforming conditions at which the charge stock exhibits substantial tendency to deactivate the catalyst, the method which comprises reforming said stock until the catalyst has lost a measurable amount of activity, discontinuing the processing of said charge stock and substituting therefor a normally liquid hydrocarbon charge stock substantially free from nitrogen compounds, and which exhibits less tendency to deactivate the fresh catalyst, reforming said latter stock until at least a part of the lost activity has been restored, and thereafter discontinuing the reforming of said latter stock and resuming the reforming of the first-mentioned stock.

References Cited in the file of this patent UNITED STATES PATENTS 2,723,946 Donaldson Nov. 15, 1955 

1. IN THE REFORMING OF A HYDROCARBON CHARGE STOCK BOILING APPROXIMATELY WITHIN THE GASOLINE RANGE AND HAVING AN APPRECIABLE NITROGEN COMPOUND CONTENT IN THE PRESENCE OF HYDROGEN AND A PLATINUM-CONTAINING CATALYST AT REFORMING CONDITIONS AT WHICH THE CHARGE STOCK EXHIBITS SUBSTANTIAL TENDENCY TO DEACTIVATE THE CATALYST, THE METHOD WHICH COMPRISES REFORMING SAID STOCK UNTIL THE CATALYST HAS LOST A MEASURABLE AMOUNT OF ACTIVITY, DISCONTINUING THE PROCESSING OF SAID CHARGE STOCK AND SUBSTITUTING THEREFOR A NORMALLY LIQUID HYDROCARBON CHARGE STOCK SUBSTANTIALLY FREE FROM NITROGEN COMPOUNDS AND WHICH EXHIBITS LESS TENDENCY TO DEACTIVATE THE FRESH CATALYST, REFORMING SAID LATTER STOCK UNTIL AT LEAST A PART OF THE LOST ACTIVITY HAS BEEN RESTORED, AND THEREAFTER DISCONTINUING THE REFORMING OF SAID LATTER STOCK AND REFORMING A CHARGE STOCK BOILING APPROXIMATELY WITHIN THE GASOLINE RANGE AND HAVING AN APPRECIABLE NITROGEN CONTENT IN THE PRESENCE OF HYDROGEN. 